The present invention relates to a magnetic recording and reproducing device for recording and reproducing information signals as oblique tracks on a magnetic tape by a rotary magnetic head.
In a magnetic recording and reproducing device for recording and reproducing information signals as oblique tracks on a magnetic tape, normally, helical scanning has heretofore been performed using a rotary magnetic head. Further, a signal to be recorded on a magnetic tape is divided according to the number of tracks to suit this reproducing system.
At this time, for example, as in the approach run interval for an after-break recording, there are cases where a reference signal is present with which the signal to be reproduced should synchronize. In such case, synchronism can be achieved by directly or indirectly comparing phases between the reference signal produced in the device and the signal reproduced from the magnetic tape, and reflecting the result on the tracking control.
In the case of a home-use VTR (such as VHS), one field is recorded as one track, and one frame as two tracks. In reproducing the same, a control (hereinafter referred to as CTL) signal (usually, one pulse per frame) is recorded in a linear track prepared separate from the oblique tracks, and tracking control is effected such that it synchronizes with the reference signal produced in the device.
Further, there is an example in which one frame is divided into 20 to 24 tracks as in a business-use VTR (D1). In this case also, a CTL track is present, and a servo signal of one pulse per drum revolution (four tracks) and a frame signal of one pulse per frame are recorded, and in the case where external synchronism is to be effected, the same control as in said home-use VTR has been performed using a frame signal, as disclosed in, e.g., a magazine xe2x80x9cBROADCASTING TECHNIQUExe2x80x9d, 1990, Vol. 43, No. 12.
Further, there is another example in which a signal for one frame is dividedly recorded on 10 tracks of a magnetic tape, as in the case of a home-use digital VTR. In the signal reproduction processing, there is a reference frame signal to be synchronized, and this reference frame signal is compared, in respect of phase, with the frame phase information reproduced from the magnetic tape, the result being reflected on the tracking control, thereby achieving synchronism for the frame.
With the aforesaid VTR, there arises a need for synchronism with the reference signal when reproduction is started. Since the synchronism pull-in speed is limited by the frame frequency, in the case of a VTR whose frame frequency is 30 Hz in NTSC it sometimes becomes impossible to attain the sufficient pull-in speed. Particularly at the time of after-break recording, since the operator gives an image recording instruction at the time he ascertains the image he intends to record, the time taken for start-frame synchronism leads to a failure in recording the image and sound.
Therefore, in order to accelerate frame synchronism from the state in which the tape stops running, there is invented a method, as disclosed, e.g., in Japanese Laid-open Unexamined Patent Application No. 7-192357, in which when a magnetic tape is stopped, its position is recorded, thereby regulating the start timing with respect to the reference signal.
This known magnetic recording and reproducing device, however, has the following disadvantages:
In the tape running state, the count of the FG pulses is reset by the reference signal produced in the device without direct connection with the recorded position on the magnetic tape, the error in detecting the position of the track relative to the head during the tape stoppage is increased due to the tracking deviation or offset. Particularly in the case of a narrow track and high density record VTR, immediate landing on a predetermined track is impossible, causing the disturbance of image immediately after the start or causing the thinning of tracks at the editing point during after-break recording.
In conventional examples, in slow reproduction of recorded signals, a special arrangement and action are required which are different than in the ordinary reproduction. For example, concerning the slow system by intermittent feed, in the conventional system for obtaining slow images by intermittently moving a magnetic tape each time by one frame or by one field, there are disadvantages in that a plurality of magnetic heads are installed on a cylinder to be selectively used according to the mode or in that a special circuit and a complicated software-wise processing are required in order to obtain a stabilized slowly reproduced image.
Further, in a VTR which intermittently records as in time-lapse recording, start and stop are repeated at predetermined intervals so as to successively record the information on a magnetic tape. In conventional examples, precision control of the position of a track to be recorded is difficult at the time of start and stop, resulting in erasing adjacent tracks during recording or in envelope chipping during reproduction, thus detracting from the quality of images. Particularly in a VTR which records at high density with small track width, this influence is so strong that in the worst case it occurs that images cannot be recorded.
Accordingly, there is a method, as disclosed in Japanese Laid-open Unexamined Patent Application No. 59-127255, in which the magnetic tape is driven backward a little, from which position it is then driven forward so as to allow recording during the period when the tape running speed is stabilized. This conventional example also, however, does not allow immediate recording with the desired timing, thus leading to a failure in recording or to a disadvantage that the arrangement is complicated.
The present invention has been accomplished with the above-mentioned disadvantages taken into consideration, and is intended to provide a magnetic recording and reproducing device which prevents the thinning of tracks at the editing point during after-break recording and also prevents the disturbance of image immediately after the start.
Another object of the invention is to provide a magnetic recording and reproducing device, with which it is possible to obtain a slowly reproduced image without requiring a special circuit or complicated software-wise processing.
Still another object of the invention is to provide a magnetic recording and reproducing device of the intermittent recording type, which which it is possible to obtain a reproduced image of high quality without causing thinning to a track to be recorded.
To achieve these objects, the magnetic recording and reproducing device of the present invention is characterized by keeping count of the FG pulses corresponding to the rotation of the capstan motor in the running state of the magnetic tape by FG pulse counting means, said count of the FG pulses being reset by the CTL signal on the magnetic tape reproduced by a fixed magnetic head, wherein at the time of start, the start timing is controlled on the basis of the tape stop position detected by the FG pulse counting means.
With such device, it is possible to prevent the thinning of tracks at the editing point during after-break recording and the disturbance of image immediately after the start.
Further, to achieve said another object, the magnetic recording and reproducing device is characterized in that the capstan motor for moving the magnetic tape is driven in synchronism with the reference signal from reference frame signal generating means, in that the magnetic tape is fed by an amount corresponding to M frames on the basis of reproduction frame phase information and then stopped for a time corresponding to N frames, whereby M/(M+N) times slower reproduction is effected.
With such device, it is possible to obtain a stabilized slowly reproduced image without requiring a special circuit or complicated software-wise processing.
To achieve said still another object, the magnetic recording and reproducing device is characterized in that at least two adjacent magnetic heads for recording tracks of different azimuth angles by a first magnetic head and a second magnetic head which follows the first are mounted on a rotary drum, the arrangement being such that the magnetic tape is stopped after termination of recording by the first and second magnetic heads, the magnetic tape being fed by an amount corresponding to two tracks from the time the first magnetic head starts recording until the time the first magnetic head starts the next recording.
According to such device, it is possible, in a magnetic recording and reproducing device for intermittent recording, to obtain a reproduced image of high quality without causing thinning to a track to be recorded.
In a preferred embodiment of the invention, a magnetic tape having a plurality of tracks and a plurality of CTL signals recorded thereon per frame is moved while the number of pulses of the FG signal corresponding to the rotation of the capstan motor are counted all the time, the count of the FG pulses being reset by the CTL signal reproduced from the magnetic tape by the fixed head, and at the time of start the start timing for the magnetic tape is controlled on the basis of the tape position detected by FG pulse counting means and CTL counting means and on the basis of a reference frame signal from reference signal generating means.
For this reason, the thinning of tracks at the editing point in the after-break recording and the disturbance of images immediately after the start are prevented, and a special circuit or a complicated software-wise processing is not required, providing a stabilized slowly reproduced image, and in a magnetic recording and reproducing device of the intermittent recording type, there is no possibility of the thinning of recorded tracks, and a high quality of image is obtained.